Structural highlights
Function[NTPA_THEMA] Pyrophosphatase that hydrolyzes non-canonical purine nucleotides such as XTP and ITP/dITP to their respective monophosphate derivatives. Might exclude non-canonical purines from DNA precursor pool, thus preventing their incorporation into DNA and avoiding chromosomal lesions.[HAMAP-Rule:MF_01405] Publication Abstract from PubMedThe hyperthermophilic bacterium Thermotoga maritima has a noncanonical nucleoside triphosphatase that catalyzes the conversion of inosine triphosphate (ITP), deoxyinosine triphosphate (dITP) and xanthosine triphosphate (XTP) into inosine monophosphate (IMP), deoxyinosine monophosphate (IMP) and xanthosine monophosphate (XMP), respectively. The k(cat)/K(m) values determined at 323 and 353 K fall between 1.31 x 10(4) and 7.80 x 10(4) M(-1) s(-1). ITP and dITP are slightly preferred over XTP. Activity towards canonical nucleoside triphosphates (ATP and GTP) was not detected. The enzyme has an absolute requirement for Mg(2+) as a cofactor and has a preference for alkaline conditions. A protein X-ray structure of the enzyme with bound IMP was obtained at 2.15 A resolution. The active site houses a well conserved network of residues that are critical for substrate recognition and catalysis. The crystal structure shows a tetramer with two possible dimer interfaces. One of these interfaces strongly resembles the dimer interface that is found in the structures of other noncanonical nucleoside pyrophosphatases from human (human ITPase) and archaea (Mj0226 and PhNTPase). Structural and functional characterization of a noncanonical nucleoside triphosphate pyrophosphatase from Thermotoga maritima.,Awwad K, Desai A, Smith C, Sommerhalter M Acta Crystallogr D Biol Crystallogr. 2013 Feb;69(Pt 2):184-93. doi:, 10.1107/S0907444912044630. Epub 2013 Jan 18. PMID:23385455[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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